Adenoviral-mediated imaging of gene transfer using a somatostatin receptor-cytosine deaminase fusion protein

• Published in: Cancer gene therapy 2015-04, Vol.22 (4), p.215-221
• Main Authors: Lears, K A, Parry, J J, Andrews, R, Nguyen, K, Wadas, T J, Rogers, B E
• Format: Article
• Language: English
• Subjects: 5-Fluorouracil; 59/78; 631/1647; Adenoviridae - genetics; Adenovirus; Analysis; Animals; Binding, Competitive; Biomedical and Life Sciences; Biomedicine; Breast cancer; Cancer; Care and treatment; Chemotherapy; Cytosine; Cytosine deaminase; Cytosine Deaminase - biosynthesis; Cytosine Deaminase - genetics; Cytotoxicity; Female; Flucytosine - pharmacokinetics; Flucytosine - therapeutic use; Fungal Proteins - biosynthesis; Fungal Proteins - genetics; Fusion protein; Gene Expression; Gene Therapy; Genes, Reporter; Genetic Therapy; Genetic transformation; Humans; MCF-7 Cells; Mice, SCID; Organ Specificity; original-article; Positron emission tomography; Prodrugs - pharmacokinetics; Prodrugs - therapeutic use; Proteins; Receptors, Somatostatin - biosynthesis; Receptors, Somatostatin - genetics; Recombinant Fusion Proteins - biosynthesis; Recombinant Fusion Proteins - genetics; Somatostatin; Somatostatin receptors; Suicide; Suicide genes; Transduction, Genetic; Xenograft Model Antitumor Assays
• ISSN: 0929-1903; 1476-5500
• DOI: 10.1038/cgt.2015.14

Suicide gene therapy is a process by which cells are administered a gene that encodes a protein capable of converting a nontoxic prodrug into an active toxin. Cytosine deaminase (CD) has been widely investigated as a means of suicide gene therapy owing to the enzyme’s ability to convert the prodrug 5-fluorocytosine (5-FC) into the toxic compound 5-fluorouracil (5-FU). However, the extent of gene transfer is a limiting factor in predicting therapeutic outcome. The ability to monitor gene transfer, non-invasively, would strengthen the efficiency of therapy. In this regard, we have constructed and evaluated a replication-deficient adenovirus (Ad) containing the human somatostatin receptor subtype 2 (SSTR2) fused with a C-terminal yeast CD gene for the non-invasive monitoring of gene transfer and therapy. The resulting Ad (AdSSTR2-yCD) was evaluated in vitro in breast cancer cells to determine the function of the fusion protein. These studies demonstrated that both the SSTR2 and yCD were functional in binding assays, conversion assays and cytotoxicity assays. In vivo studies similarly demonstrated the functionality using conversion assays, biodistribution studies and small animal positron-emission tomography (PET) imaging studies. In conclusion, the fusion protein has been validated as useful for the non-invasive imaging of yCD expression and will be evaluated in the future for monitoring yCD-based therapy.